This invention relates to mail retaining apparatus and in particular to apparatus for retaining a mail piece in a position in which it has been placed for printing a postal indicia thereon.
Postal authorities require that postal indicia are printed in a specified area adjacent an upper right hand corner of mail pieces. Accordingly, in printing devices for printing postal indicia on mail pieces, it is necessary that the mail piece be correctly located relative to a print head to ensure that the postal indicia is printed in the specified area on the mail piece.
In postage metering apparatus intended to handle a relatively small throughput of mail pieces, the mail pieces are inserted manually into the postage metering apparatus and must be correctly located manually relative to a field of the apparatus in which printing is to be effected. Guides provided for engagement by mail pieces are located such that when the mail piece engages the guides, the mail piece is correctly located with the area of the mail piece required to receive the postal indicium imprint aligned with the printing field. Mail detection means is provided to respond to a mail piece being manually located in engagement with the guides and thus to provide an output signal indicating that the specified area on the mail piece for a postage indicium imprint is aligned with the print field of the postage metering apparatus. It will be appreciated that, when the mail piece has been correctly located for printing the postal indicium, the mail piece must be maintained in the correct location until printing of the indicium has been completed. If the mail piece is subjected to displacement away from the correct location thereof prior to commencement of printing the postal indicium will not be printed in the specified location on the mail piece. Also commonly used digital print heads operate in a series of print cycles in each of which cycles dots to form parts of the imprint are printed in selected positions in a series of columns spaced across the print field. Accordingly if any displacement of the mail piece occurs during the series of print cycles, a distorted postal indicium will be printed.
The dimensions of mail pieces may have a substantial range of sizes. Accordingly in order to facilitate location of mail pieces with the upper right hand corner thereof located so as to receive a postal indicium imprint in the specified area thereon a slot for reception of mail pieces is open both to the front and to the left hand side of the postage metering apparatus whereby mail pieces may extend from the slot from the front and from the left hand side of the apparatus. A user of the postage metering apparatus may enter the mail into the slot of the postage metering apparatus from the front, from the left hand side or in any direction therebetween. Our pending unpublished UK patent application No. 9902062.0 describes and claims a mail sensor that responds to correct location of the mail regardless of which of the directions the mail piece is entered into the slot.
In order to ensure correct functioning of the print head a surface of the mail piece that is to receive the postal indicium imprint needs to be located at a required distance from the print head of the postage metering apparatus. Accordingly the mail piece is resiliently urged against a guide so that the postal indicium receiving surface of the mail piece lies in a plane with a predetermined spacing from the print head. Preferably the print head is an ink jet digital print head in which droplets of ink are ejected selectively from nozzles of the print head to the surface of the mail piece however other types of print head may be utilised, for example the print head may be a digital impact print head in which tips of print wires are impacted selectively with an ink ribbon to transfer ink from the ribbon to the surface of the mail piece.
A construction of apparatus for supporting and maintaining a mail piece in a required location relative to a print head is described in our pending UK patent application No. 9902062.0. A mail piece when inserted into the postage metering apparatus is supported by a platform and the platform is resiliently urged toward an apertured guide plate so that the postal indicium receiving surface of the mail piece is located in engagement with the guide plate at a required spacing from the print head. The resilient urging of the platform toward the guide plate, with the mail piece located between the platform and the guide plate, serves to clamp the mail piece. The platform is displaceable to an open position in which the platform is spaced from the guide plate by a distance sufficient to permit entry of a mail piece between the platform and the guide plate and to permit removal of a mail piece therefrom. When a mail piece has been entered between the platform and guide plate and the mail piece is correctly located in engagement with the guides, the mail sensing means outputs a signal and, in response to this signal, the platform is urged toward the guide plate by resilient means thereby clamping the mail piece between the platform and the guide plate.
It will be appreciated that the mail piece may be entered between the platform and guide plate and be correctly located in engagement with the guides so that the mail sensing means output signal initiates the urging of the platform toward the guide plate but, before the mail piece has been clamped between the platform and the guide plate, the mail piece accidentally may be displaced from the correct location thereof. As a result the mail piece will be clamped in a location displaced from the correct location and the imprint of the postal indicium will be incorrectly located on the mail piece. Therefore the present invention provides means resisting displacement of the mail piece after the mail piece has been correctly located at least until the mail piece has been secured by clamping between the platform and the guide plate.
According to the invention apparatus for retaining a mail piece includes first and second clamp elements, said clamp elements having an open state in which the first clamp element is spaced from said second clamp element for insertion of a mail item therebetween into a required position in which a predetermined part of the mail piece is located at a predetermined location and a closed state in which at least one of said first and second clamp elements is displaced toward the other of said first and second clamp elements to clamp the mail piece and further including mail piece retention means mounted on said first clamp element and effective during displacement of said at least one clamp element to retain said mail piece in said required position to which it has been inserted.